The present invention relates to priming of thermal ink jet printheads and, more particularly, to a priming system located at a maintenance station for a multicolor ink jet printer having at least one peristaltic priming pump which selectively primes either a black ink printing printhead or a color ink printing printhead.
Thermal ink jet printing systems use thermal energy pulses generated by the heating elements in an ink jet printhead to produce momentary ink vapor bubbles on the heating elements which eject ink droplets from the printhead nozzles. One type of such a printhead has a plurality of parallel ink channels, each communicating at one end with an ink reservoir and having opposing open ends which serve as nozzles on the droplet emitting face of the printhead. A heating element, usually a resistor, is located in each of the ink channels a predetermined distance upstream from the nozzle openings. The heating elements are individually driven with a current pulse to momentarily vaporize the ink and form a bubble which expels a droplet of ink. The channel is then refilled by capillary action, drawing ink from a supply tank. A meniscus is formed at each nozzle under a slight negative pressure to prevent ink from weeping therefrom. Operation of a thermal ink jet printer is described, for example, in U.S. Pat. No. 4,849,774 and U.S. Pat. No. 4,571,599.
The carriage type ink jet printer, of which the present invention relates, typically has one or more small printheads containing the ink channels and nozzles in a nozzle face. The printheads are connected to an ink supply tank. In one configuration, the printhead and one or more ink tanks are integrally assembled and the entire configuration, sometimes referred to as a cartridge, is disposable when the ink in the ink tanks are depleted. In another configuration, the printhead is an integral part of a replaceable ink tank support and replaceable ink supply tanks are installed on the ink tank support. Generally, the ink tank support is first installed on the printer""s translatable carriage and then the ink supply tanks are installed. Each of the ink supply tanks is replaced when the ink contained therein is depleted. The replaceable ink tank support should not need to be replaced until at least ten ink supply tanks have been emptied during printing operations.
For carriage type multicolor ink jet printers of the latter type, there is a replaceable ink tank support for printing black ink and a separate replaceable ink tank support for printing non-black inks. These ink tank supports are installed on the printer""s carriage and then the respective ink tanks are installed on the appropriate ink tank support. Whether the carriage type ink jet printer uses replaceable cartridges comprising integral printheads and ink supply tanks or replaceable ink tank supports with integral printheads and separate replaceable ink tanks, both types are translated in a printing zone in one direction to print a swath of information on a recording medium, such as paper. The swath height is equal to the length of the column of nozzles in the printhead""s nozzle face. The paper is held stationary during the printing and, after the swath is printed, the paper is stepped a distance equal to the height of the printed swath or a portion thereof. This procedure is repeated until the entire page is printed or until all information has been printed, if less than a page. For an example of a typical ink cartridge, refer to U.S. Pat. No. 5,519,425 which discloses disposable ink cartridges having integral printheads and ink supply tanks, and refer to U.S. Pat. No. 5,971,531 for a replaceable ink tank support having integral printheads and separately replaceable ink supply tanks.
As is well known, the thermal ink jet printheads of the carriage type printers require maintenance usually at a maintenance station located to one side of the printing zone, where the printhead nozzle faces are periodically cleaned during and after a printing operation. At the completion of a printing operation, the printhead is translated by the carriage to the maintenance station where the printhead nozzle face is sealingly covered by a cap to keep the ink in the nozzles from drying out. In addition, the printhead may be primed while capped to ensure that the printhead channels are completely filled with ink and contain no print inhibiting air bubbles. The non-used or little used nozzles may be cleared by translating the printhead to the maintenance station and ejecting ink droplets from those nozzles into, for example, a xe2x80x98spittoonxe2x80x99 or the cap. The cleaning of the printhead nozzle faces are generally accomplished by using wiper blades which wipe the nozzle faces as they enter and/or leave the maintenance station. Refer to U.S. Pat. No. 5,404,158 for a typical maintenance station.
In many existing thermal ink jet printers, peristaltic pumps have been used to effect priming of a capped printhead, where priming is defined as filling the flow paths of the printhead and other ink flow passageways between the printhead nozzles and the ink supply tank. Although the priming can be done by temporarily using positive pressure on the ink in the ink tank to force ink and entrained air and/or air bubbles out of the ink flow paths, it is more popular to use a vacuum or suction on the nozzles to withdraw some ink and thus any trapped air from the printhead.
U.S. Pat. No. 6,220,699 discloses a printer apparatus and method of actuating a fluid pump to deliver fluid to an ink jet printhead without removing the printhead from a printhead carriage that is particularly useful for priming ink jet printheads using an air displacement pump to deliver air under positive pressure to the printheads. The pump is located proximate a maintenance station on the printer and is automatically actuated by movement of the carriage to the maintenance station.
U.S. Pat. No. 5,572,243 discloses a priming element for priming or maintaining the nozzles or orifices of an ink jet printer. The priming element applies a vacuum or negative pressure generated by a suction device to the nozzles. The priming element includes a first wall and a second wall spaced from the first wall to define a passageway between the first wall and the second wall. One or more support members connect the first wall to the second wall and span the passageway to prevent the walls of the priming element from collapsing from the applied vacuum or negative pressure.
U.S. Pat. No. 5,757,398 discloses a liquid ink printer forming images on a recording medium including a liquid ink printhead movable between a printing position and a maintenance position and a maintenance arrangement, located at the maintenance position, including a driver, a first mechanism and a second mechanism. The driver is coupled to the first mechanism and to the second mechanism and moves in a first direction to actuate the first mechanism and in a second direction to actuate the second mechanism. The driver includes a stepper motor having a single shaft coupled to the first mechanism, such as a cam bank or rotary valve, and to the second mechanism, such as a vacuum pump, through a unidirectional clutch.
U.S. Pat. No. 6,130,684 discloses an ink jet printer which includes a capping and wiping system in a maintenance station that is connected to a common vacuum source. The wiping system includes a blotter type collection member which presents an air vent when the printhead is in a capped position. When a priming operation is initiated, the air vent route is blocked, and full pressure is applied at the capping nozzle interface.
In one known multicolor ink jet printer, the printhead is primed at the maintenance station by evacuating the cap while it sealingly covers the printhead nozzle face. A typical system to prime printheads using a vacuum or negative pressure is to place a peristaltic pump in a line interconnecting the waste ink collector to the cap. Using this technique in a multicolor ink jet printer requires that both the printhead which prints with black ink and the printhead which prints with non-black ink, i.e., cyan, magenta, and yellow inks, were primed concurrently when only one or the other of the printheads actually needed to be primed. This failure to be able to individually prime the printheads increases the amount of ink wasted by priming, thereby reducing the total number of printed pages the customer could get from an ink tank.
It is an object of the present invention to provide an improved priming system for a multicolor ink jet printer by eliminating the concurrent priming of both the black ink printing printhead and the color or non-black ink printing printhead when only one printhead requires priming. This is accomplished by two individual peristaltic pumps having a single mechanical input which selectively drives the pumps. This system thus separates the vacuum necessary to prime one printhead from the other by using the direction of the single mechanical input, coupled with a swing gear, as the means to control the operation of one pump and render the other pump inoperable.
In one aspect of the present invention, there is provided a priming system for a multicolor ink jet printer having a black ink printing printhead and a non-black ink printing printhead mounted on a translatable carriage for concurrent movement therewith, the translatable carriage being translated across a printing zone during a printing operation and being translated to a maintenance station when the printer is in a non-printing operation for printhead cleaning and capping of each printhead by a separate cap, the priming system comprising: two individual peristaltic pumps, each of said pumps having a tube therethrough, one end of the tubes being connected to a waste ink collector, each of the other ends of the tubes being connected to a respective one of the caps in said maintenance station, one of said pumps being operable when driven in a first direction and the other of said pumps being operable when driven in a second direction; a positionable swing gear being selectively positioned into driving engagement with a selected one of said pumps; a drive gear being in continual driving engagement with said swing gear; and a bi-directional drive means for selectively driving the drive gear in either a first or a second direction to selectively effect operation of the desired one of the pumps to produce a vacuum between the selected printhead and said pump, thereby preventing concurrent priming of both printheads when only one printhead requires priming.